Why doesn't Thumbelina just use the bird to get home?
Jacquimo was too concerned with reuniting Thumbelina and Cornelius (via locating the Vale of the Fairies) to actually just take her home. She does ask him to do so several times, but he ignores her.
But then why doesn't he reunite them by flying Thumbelina to Cornelius, or flying her home and then flying him there? True, he wasn't sure where Cornelius was, but he could have let her ride while searching or dropped her off at home, then searched for him, then brought him to her home upon finding him.
Sadly, the writers were kind of locked-in to the original story and never fully explained why didn't she get off the lilypad by herself.
Adaption Induced Plothole. They wanted to introduce elements like the bird and the fairies a lot earlier so they felt less contrived and tacked on, but of course in Jaquimo's case this created a huge plot hole the movie had no way of dealing with. Although considering how absent-minded Jaquimo is portrayed, you could believe that he simply forgot he could fly her home.
How come Mrs. Toad sings about why marriage sucks to get Thumbelina to marry her son?
Mrs. Toad seemed to be trying to convince Thumbelina that marrying for love would suck, but that the marriage she had planned out (which seemed more like a convenient way to please her son and get a good singer into their family performing group) was awesome. One can only hope that Mrs. Toad was figuring that Thumbelina would forgo child with her toad son in favor of focusing on their career.
Ignoring the fact that Thumbelina and Cornelius hardly knew each other, how the heck does the moral of marrying for love over money work? Cornelius is the fairy prince! Are we really to believe that he doesn't have enough money to support a family, or servants to raise the kids, or whatever else the arguments against him were?
She fell in love with him before she knew he was the fairy prince, and she seems to think of the prince less in terms of being rich than in terms of "who you're supposed to get together with in order to have a happy ending."
Plus, an fairy would probably not reckon wealth the same way as humans. Cornelius may have power, influence, and be rich in real possessions, but I doubt that he has much in the way of cash lying around.
At the part of Yer Beautiful Baby where the bugs are insulting Thumbelina, you can hear Beetle singing a second verse in the background. Anyone know what the words are? This is all I can make out:
Sometimes baby fire flies
A hornet’s fire flies [da-da-da]
Some may get up with [da da-da]
But what matters [da da da-da-da]
I beg to diff/cause you’re terrif!”
Even the soundtrack version masks them. What is the point of doing that?
Why did the toads drive off and leave Thumbelina on a lilypad when they wanted her to marry Grundel?
Because Andersen said so. No really, it's from the original story. The mother toad and son leave Thumbelina on the lily pad so they can fetch their relatives for the upcoming nupitals. Of course in the original they didn't have a frickin' ass boat they could've just kept her on. She escapes not by bird but by some fish who take pity and nibble the lily pad free then push her to shore.